Recently, attention has been paid to a hybrid vehicle or a variety of industrial devices realizing low power consumption by accumulating regenerative electric power during braking or the like in an electric double layer capacitor or the like.
Such a device requires a circuit module dealing with high current such as a DC/DC converter (which converts a DC input into a DC output) controlling high current exceeding 100 A with high accuracy. It is necessary to mount a power semiconductor and the like used in this module on a heat dissipation board that can deal with heat dissipation and high current.
As a heat dissipation board of this type, there is known a metal-based printed circuit board structured to bond a printed circuit board onto a metal board via an insulating adhesive layer that contains a metal oxide and/or a metal nitride in Patent Document 1.
FIG. 34 is a cross-sectional view showing an example of a conventional heat dissipation board. In FIG. 34, conductor circuit 3 is fixed onto metal board 1 via first insulating adhesive layer 2. Conductor layer for circuit (“circuit conductor layer”) 5 is further formed on conductor circuit 3 via second insulating adhesive layer 8. Conductor circuit 3 is connected to circuit conductor layer 5 by via hole 6. However, there is a limit to such a conventional heat dissipation board for reinforcing a peel strength of circuit conductor layer 5.
For example, when a part of circuit conductor layer 5 is formed as an external lead terminal part and pulled as indicated by arrow 7, it is only an adhesive force of insulating adhesive layer 8 that resists this “tensile force”. As a result, it is difficult to deal with vibration resistance (for example, an acceleration test of about 4 G to 20 G is conducted in XYZ directions) as required for on-vehicle devices. Furthermore, even if a thick material such as a lead frame that can deal with a high current and that has a high strength is employed for conductor circuit 3 and circuit conductor layer 5, similar problems occur.
In this way, in the conventional heat dissipation board, circuit conductor layer 5 that is an outermost layer is only adhesively bonded onto a surface of second insulating adhesive layer 8. Due to this, if a high strength is applied to this layer via the printed board or a power cable, an adhesive surface (or an interface) of the layer is possibly peeled off.
On the other hand, it is demanded to mount a semiconductor chip main body (such as a bare chip) in place of a resin-molded semiconductor using such a mounting method as wire bonding so as to make a circuit module smaller in size and lighter in weight.
To meet the demand, there is proposed bare chip mounting for a semiconductor in Patent Document 2. However, it is difficult for a conventional semiconductor module to deal with mounting of a large-sized electronic component or an odd-shaped electronic component such as a transformer or a choke coil and the electronic component is possibly detached from the semiconductor module due to vibration or the like.
Moreover, there is also proposed a structure of setting a control printed circuit board almost in parallel on a bare-chip-mounted power semiconductor in Patent Document 2. However, it is difficult for the proposed structure to deal with mounting of a large-sized electronic component or an odd-shaped electronic component such as a transformer or a choke coil.    Patent Document 1: Japanese Patent Application No. H09-139580    Patent Document 2: Japanese Patent No. 3,898,158